Metal-air battery having cylindrical structure

ABSTRACT

A metal-air battery includes a unit cell wound into a roll. The unit cell includes a negative-electrode metal layer having a first surface located in a circumferential direction of the roll and a second surface facing the first surface and located in the circumferential direction of the roll; a first electrolyte film and a first positive-electrode layer sequentially disposed on the first surface of the negative-electrode metal layer; and a second electrolyte film and a second positive-electrode layer sequentially disposed on the second surface of the negative-electrode metal layer. The unit cell is wound in a way such that the first positive-electrode layer and the second positive-electrode layer face each other.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Korean Patent Application No.10-2016-0127142, filed on Sep. 30, 2016, and all the benefits accruingtherefrom under 35 U.S.C. § 119, the content of which in its entirety isherein incorporated by reference.

BACKGROUND 1. Field

Embodiments set forth herein relate to a metal-air battery, and moreparticularly, to a cylindrical metal-air battery having improved energydensity.

2. Description of the Related Art

A metal-air battery typically includes a negative electrode capable ofintercalating/deintercalating ions and a positive electrode that usesoxygen from an outside, e.g., in the air, as an active material. In themetal-air battery, reduction and oxidation reactions of oxygen receivedfrom the outside occur in the positive electrode, oxidation andreduction reactions of the metal occur in the negative electrode, andchemical energy generated to be extracted as electrical energy. Themetal-air battery absorbs oxygen during discharge and emits oxygenduring charge. As described above, since the metal-air battery usesoxygen in the air as an active material, the energy density of themetal-air battery may be greater than those of other batteries. Forexample, the metal-air battery may have an energy density several timeshigher than that of a conventional lithium ion battery.

In addition, since the metal-air battery has a low probability ofigniting due to an abnormally high temperature, the metal-air battery ishighly stable and, since the metal-air battery is only operated byintercalation and deintercalation of oxygen without using a heavy metal,there is a low probability of environmental contamination by themetal-air battery. Due to such various desired features, much researchinto the metal-air battery is currently being performed.

SUMMARY

According to an embodiment, a metal-air battery includes a unit cellwound into a roll. In such an embodiment, the unit cell includes anegative-electrode metal layer having a first surface located in acircumferential direction of the roll, and a second surface facing thefirst surface and located in the circumferential direction of the roll;a first electrolyte film and a first positive-electrode layersequentially disposed on the first surface of the negative-electrodemetal layer; and a second electrolyte film and a secondpositive-electrode layer sequentially disposed on the second surface ofthe negative-electrode metal layer. In such an embodiment, the unit cellis wound in a way such that the first positive-electrode layer and thesecond positive-electrode layer face each other.

In an embodiment, the first electrolyte film and the second electrolytefilm may be continuously connected to each other. The firstpositive-electrode layer and the second positive-electrode layer may becontinuously connected to each other.

In an embodiment, the negative-electrode metal layer may have a thirdsurface between the first surface and the second surface, and a fourthsurface facing the third surface. In such an embodiment, the firstelectrolyte film and the second electrolyte film may be connected toeach other to surround the third surface of the negative-electrode metallayer.

In an embodiment, the first positive-electrode layer and the secondpositive-electrode layer may be connected to each other to surround thethird surface of the negative-electrode metal layer.

In an embodiment, the unit cell may further include a first separationfilm disposed between the first electrolyte film and the firstpositive-electrode layer; and a second separation film disposed betweenthe second electrolyte film and the second positive-electrode layer. Insuch an embodiment, the first separation film and the second separationfilm may be continuously connected to each other to surround the thirdsurface of the negative-electrode metal layer.

In an embodiment, the unit cell may further include a negative-electrodecurrent collector connected to the fourth surface of thenegative-electrode metal layer.

In an embodiment, the unit cell may further include a sealing materialwhich seals the fourth surface of the negative-electrode metal layer.

In an embodiment, the unit cell may be wound in the way such that thethird surface of the negative-electrode metal layer is located at acenter of the roll and the fourth surface of the negative-electrodemetal layer is located at an outermost part of the roll.

In an embodiment, the unit cell may further include a firstgas-diffusion layer disposed on the first positive-electrode layer; anda second gas-diffusion layer disposed on the second positive-electrodelayer. In such an embodiment, the first gas-diffusion layer and thesecond gas-diffusion layer may be continuously connected to each other,and the unit cell may be wound in the way such that the firstgas-diffusion layer and the second gas-diffusion layer face each other.

In an embodiment, the first electrolyte film and the second electrolytefilm may be spaced apart from each other. The first positive-electrodelayer and the second positive-electrode layer may be spaced apart fromeach other.

In an embodiment, the negative-electrode metal layer may have a thirdsurface between the first surface and the second surface, and a fourthsurface facing the third surface. In such an embodiment, the first andsecond positive-electrode layers may extend beyond the third and fourthsurfaces of the negative-electrode metal layer.

In an embodiment, the unit cell may further include a first separationfilm disposed between the first electrolyte film and the firstpositive-electrode layer; and a second separation film disposed betweenthe second electrolyte film and the second positive-electrode layer. Insuch an embodiment, the first and second separation films may be spacedapart from each other and extend beyond the third and fourth surfaces ofthe negative-electrode metal layer.

In an embodiment, the unit cell may further include a sealing materialwhich seals the third and fourth surfaces of the negative-electrodemetal layer.

In an embodiment, the unit cell may further include a negative-electrodecurrent collector connected to the fourth surface of thenegative-electrode metal layer and extending through the sealingmaterial.

In an embodiment, the unit cell may further include a firstgas-diffusion layer disposed on the first positive-electrode layer; anda second gas-diffusion layer disposed on the second positive-electrodelayer. In such an embodiment, the first and second gas-diffusion layersmay be separated from each other. In such an embodiment, the unit cellmay be wound in the way such that the first and second gas-diffusionlayers face each other.

In an embodiment, the first positive-electrode layer may include aplurality of first positive-electrode plates arranged in thecircumferential direction of the roll. In such an embodiment, a firstgap may be defined between each two adjacent first positive-electrodeplates. In such an embodiment, the second positive-electrode layer mayinclude a plurality of second positive-electrode plates arranged in thecircumferential direction of the roll. In such an embodiment, a secondgap may be defined between each two adjacent second positive-electrodeplates. In such an embodiment, the roll may be wound in a way such thatthe second positive-electrode plates connect the two adjacent firstpositive-electrode plates across the first gap.

In an embodiment, the metal-air battery may include a plurality of unitcells wound into the roll. In such an embodiment, the plurality of unitcells may be stacked in a way such that central axes of the roll do notcoincide with one another and outer circumference surfaces of the rollare in contact with one another.

In an embodiment, the metal-air battery may include a plurality of unitcells wound into the roll. In such an embodiment, the plurality of unitcells may be stacked in a way such that central axes of the rollcoincide with one another.

According to another embodiment, a metal-air battery includes a firstcylindrical part and a second cylindrical part arranged in a concentricform to share a central axis. In such an embodiment, each of the firstcylindrical part and the second cylindrical part includes a unit cell.In such an embodiment, the unit cell of each of the first cylindricalpart and the second cylindrical part includes a negative-electrode metallayer having a first surface located in a circumferential direction, anda second surface facing the first surface and located in thecircumferential direction; a first electrolyte film and a firstpositive-electrode layer sequentially disposed on the first surface ofthe negative-electrode metal layer; and a second electrolyte film and asecond positive-electrode layer sequentially disposed on the secondsurface of the negative-electrode metal layer.

In an embodiment, the unit cell of the first cylindrical part may have acylindrical shape, and the unit cell of the second cylindrical part mayhave a cylindrical shape. In such an embodiment, the secondpositive-electrode layer, the second electrolyte film, thenegative-electrode metal layer, the first electrolyte film and the firstpositive-electrode layer of the unit cell of each of the firstcylindrical part and the second cylindrical part may be arranged in aconcentric form.

In an embodiment, In the unit cell of each of the first cylindrical partand the second cylindrical part, the second electrolyte film may bedisposed to surround the second positive-electrode layer, thenegative-electrode metal layer may be disposed to surround the secondelectrolyte film, the first electrolyte film may be disposed to surroundthe negative-electrode metal layer, and the first positive-electrodelayer may be disposed to surround the first electrolyte film.

In an embodiment, the second positive-electrode layer of the unit cellof the first cylindrical part and the first positive-electrode layer ofthe unit cell may of the second cylindrical part share a commonpositive-electrode plate.

In an embodiment, the first cylindrical part may include a plurality ofunit cells arranged in the circumferential direction.

In an embodiment, in each of the plurality of unit cells of the firstcylindrical part, the negative-electrode metal layer may have a thirdsurface between the first surface and the second surface, and a fourthsurface facing the third surface. In such an embodiment, the firstelectrolyte film and the second electrolyte film may be connected toeach other to surround the third and fourth surfaces of thenegative-electrode metal layer. In such an embodiment, the firstpositive-electrode layer and the second positive-electrode layer may beconnected to each other to surround the third and fourth surface of thenegative-electrode metal layer.

In an embodiment, the third surface and the fourth surface may belocated in a direction of a diameter of the metal-air battery.

In an embodiment, the first cylindrical part may include a single unitcell having a cylindrical shape, and the second cylindrical part mayinclude a plurality of unit cells arranged in the circumferentialdirection.

In an embodiment, the unit cell of each of the first cylindrical partand the second cylindrical part may further include a first separationfilm disposed between the first electrolyte film and the firstpositive-electrode layer; and a second separation film disposed betweenthe second electrolyte film and the second positive-electrode layer.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other features will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a schematic cross-sectional view of a unit cell of a metal-airbattery according to an embodiment;

FIG. 2 is a schematic cross-sectional view of a unit cell of a metal-airbattery according to an alternative embodiment;

FIG. 3 is a schematic cross-sectional view of a unit cell of a metal-airbattery according to another alternative embodiment;

FIG. 4 is a schematic cross-sectional view of a unit cell of a metal-airbattery according to another alternative embodiment;

FIG. 5 is a schematic cross-sectional view of a unit cell of a metal-airbattery according to another alternative embodiment;

FIG. 6A is a perspective view of a metal-air battery having a rolledcylindrical shape formed by winding the unit cell of FIG. 1 into a roll;

FIG. 6B is an enlarged view of the encircled portion of FIG. 6A;

FIG. 7 is a perspective view of a metal-air battery having a rolledcylindrical shape formed by winding the unit cell of FIG. 4 into a roll;

FIG. 8 is a cross-sectional view of a metal-air battery including anouter casing;

FIG. 9 is a graph showing energy density of the metal-air battery ofFIG. 6 according to an embodiment and energy density of a conventionalmetal-air battery;

FIG. 10 is a schematic cross-sectional view of a unit cell of ametal-air battery according to another alternative embodiment;

FIG. 11 is a cross-sectional view of a part of a metal-air batteryhaving a rolled cylindrical shape formed by winding the unit cell ofFIG. 10 into a roll;

FIG. 12 is a schematic cross-sectional view of a unit cell of ametal-air battery according to another alternative embodiment;

FIG. 13 is a cross-sectional view of a metal-air battery including theunit cell of FIG. 12;

FIG. 14 is a schematic cross-sectional view of a unit cell of ametal-air battery according to another alternative embodiment;

FIG. 15 is a cross-sectional view of a metal-air battery including theunit cell of FIG. 14;

FIG. 16 is a perspective view illustrating a state in which a pluralityof metal-air batteries is stacked, according to an embodiment;

FIG. 17 is a cross-sectional view illustrating a state in which themetal-air batteries of FIG. 16 is packaged; and

FIG. 18 is a perspective view illustrating a state in which a pluralityof metal-air batteries is stacked, according to an alternativeembodiment.

DETAILED DESCRIPTION

The invention now will be described more fully hereinafter withreference to the accompanying drawings, in which various embodiments areshown. This invention may, however, be embodied in many different forms,and should not be construed as limited to the embodiments set forthherein. Rather, these embodiments are provided so that this disclosurewill be thorough and complete, and will fully convey the scope of theinvention to those skilled in the art. Like reference numerals refer tolike elements throughout.

It will be understood that when an element is referred to as being “on”another element, it can be directly on the other element or interveningelements may be present therebetween. In contrast, when an element isreferred to as being “directly on” another element, there are nointervening elements present.

It will be understood that, although the terms “first,” “second,”“third” etc. may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer or section from another element, component, region, layer orsection. Thus, “a first element,” “component,” “region,” “layer” or“section” discussed below could be termed a second element, component,region, layer or section without departing from the teachings herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms, including “at least one,” unless the content clearly indicatesotherwise. “Or” means “and/or.” As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items. It will be further understood that the terms “comprises”and/or “comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or“top,” may be used herein to describe one element's relationship toanother element as illustrated in the Figures. It will be understoodthat relative terms are intended to encompass different orientations ofthe device in addition to the orientation depicted in the Figures. Forexample, if the device in one of the figures is turned over, elementsdescribed as being on the “lower” side of other elements would then beoriented on “upper” sides of the other elements. The exemplary term“lower,” can therefore, encompasses both an orientation of “lower” and“upper,” depending on the particular orientation of the figure.Similarly, if the device in one of the figures is turned over, elementsdescribed as “below” or “beneath” other elements would then be oriented“above” the other elements. The exemplary terms “below” or “beneath”can, therefore, encompass both an orientation of above and below.

“About” or “approximately” as used herein is inclusive of the statedvalue and means within an acceptable range of deviation for theparticular value as determined by one of ordinary skill in the art,considering the measurement in question and the error associated withmeasurement of the particular quantity (i.e., the limitations of themeasurement system).

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Exemplary embodiments are described herein with reference to crosssection illustrations that are schematic illustrations of idealizedembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, embodiments described herein should not beconstrued as limited to the particular shapes of regions as illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, a region illustrated or described asflat may, typically, have rough and/or nonlinear features. Moreover,sharp angles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present claims.

Hereinafter, embodiments of a cylindrical metal-air battery will bedescribed in detail with reference to the accompanying drawings.

FIG. 1 is a schematic cross-sectional view of a unit cell of a metal-airbattery according to an embodiment.

Referring to FIG. 1, an embodiment of a unit cell 10 may include anegative-electrode metal layer 11, a first electrolyte film 12 adisposed on a top surface of the negative-electrode metal layer 11, afirst separation film 13 a disposed on a top surface of the firstelectrolyte film 12 a, a first positive-electrode layer 14 a disposed ona top surface of the first separation film 13 a, a second electrolytefilm 12 b disposed on a bottom surface of the negative-electrode metallayer 11, a second separation film 13 b disposed on a bottom surface ofthe second electrolyte film 12 b, and a second positive-electrode layer14 b disposed on a bottom surface of the second separation film 13 b.

In such an embodiment, as illustrated in FIG. 1, the first electrolytefilm 12 a and the second electrolyte film 12 b further extend to a firstside surface of the negative-electrode metal layer 11 between the topand bottom surfaces of the negative-electrode metal layer 11, and arecontinuously connected to each other to surround the first side surfaceof the negative-electrode metal layer 11. In such an embodiment, thefirst separation film 13 a and the second separation film 13 b furtherextend to the first side surface of the negative-electrode metal layer11, and are continuously connected to each other to surround the firstside surface of the negative-electrode metal layer 11. The firstpositive-electrode layer 14 a and the second positive-electrode layer 14b further extend to the first side surface of the negative-electrodemetal layer 11, and are continuously connected to each other to surroundthe first side surface of the negative-electrode metal layer 11. In suchan embodiment, the first electrolyte film 12 a and the secondelectrolyte film 12 b collectively define an electrolyte film 12, thefirst separation film 13 a and the second separation film 13 bcollectively define a separation film 13, and the firstpositive-electrode layer 14 a and the second positive-electrode layer 14b collectively define a positive-electrode layer 14. Thus, the firstside surface of the negative-electrode metal layer 11 is surrounded bythe electrolyte film 12, the separation film 13, and thepositive-electrode layer 14, and only a second side surface thereofopposite to the first side surface may be exposed to an outside. Anegative-electrode current collector 15 may be further disposed in theexposed second side surface of the negative-electrode metal layer 11,through which current is drawn to the outside.

FIG. 2 is a schematic cross-sectional view of a unit cell of a metal-airbattery according to an alternative embodiment.

Referring to FIG. 2, in such an embodiment, a first separation film 13 aand a second separation film 13 b of a unit cell 10′ may extend orprotrude beyond a second side surface of a negative-electrode metallayer 11. A gap or a space between protruding portions of the firstseparation film 13 a and the second separation film 13 b over the secondside surface of the negative-electrode metal layer 11 may be filled witha sealing material 16 to seal the second side surface of thenegative-electrode metal layer 11, thereby effectively preventingcontact of the negative-electrode metal layer 11 with air. In such anembodiment, the negative-electrode current collector 15 may be connectedto the second side surface of the negative-electrode metal layer 11 andextend through the sealing material 16.

The negative electrode metal layer 11 capable ofintercalating/deintercalating metal ions may include or be formed of,for example, lithium (Li), sodium (Na), zinc (Zn), potassium (K),calcium (Ca), magnesium (Mg), iron (Fe), aluminum (Al), or an alloythereof.

The first and second electrolyte films 12 a and 12 b transfer metal ionsto the first and second positive-electrode layers 14 a and 14 b,respectively. To transfer metal ions to the first and secondpositive-electrode layers 14 a and 14 b, the first and secondelectrolyte films 12 a and 12 b may include an electrolyte formed bydissolving a metal salt in a solvent. In general, the electrolyte may bein a solid state and includes a polymer-based electrolyte, an inorganicelectrolyte, or a composite electrolyte obtained from a mixture thereof,and is manufactured to be flexible so that the electrolyte may be easilybent. In one embodiment, for example, the metal salt may be, forexample, lithium salt such as LiN(SO₂CF₂CF₃)₂, LiN(SO₂C₂F₅)₂, LiClO₄,LiBF₄, LiPF₆, LiSbF₆, LiAsF₆, LiCF₃SO₃, LiN(SO₂CF₃)₂, LiC(SO₂CF₃)₃,LiN(SO₃CF₃)₂, LiC₄F₉SO₃, LiAlCl₄, or lithiumbis(trifluoromethanesulfonyl)imide (“LiTFSI”). Another metal salt suchas AlCl₃, MgCl₂, NaCl, KCl, NaBr, KBr, or CaCl₂ may be added to thelithium salt. Any material that may dissolve the lithium salt and themetal salt may be used as the solvent.

The first and second separation films 13 a and 13 b have conductivitywith respect to metal ions while preventing penetration of oxygen. Thefirst and second separation films 13 a and 13 b may be flexiblepolymer-based separation films. In one embodiment, for example, thefirst and second separation films 13 a and 13 b may include or be formedof polymer non-woven fabric such as non-woven fabric of polypropylene ornon-woven fabric of polyphenylene sulfide, a porous film of olefin-basedresin such as polyethylene or polypropylene, or the like.

Although FIGS. 1 and 2 illustrate embodiments where the first and secondelectrolyte films 12 a and 12 b and the first and second separationfilms 13 a and 13 b are separately defined, the first and secondelectrolyte films 12 a and 12 b or the first and second separation films13 a and 13 b may be formed in a single unitary layer by impregnatingpores of porous separation films with an electrolyte. In such anembodiment, the first electrolyte film 12 a and the first separationfilm 13 a may be formed in a single layer, and the second electrolytefilm 12 b and the second separation film 13 b may be formed in a singleunitary layer. In one embodiment, for example, a separation film or anelectrolyte film may be formed in a single unitary layer by impregnatingpores of porous separation films with an electrolyte formed by mixingpolyethylene oxide (“PEO”) with LiTFSI.

The first and second positive-electrode layers 14 a and 14 b may includean electrolyte for conduction of metal ions, a catalyst for reductionand oxidation reactions of oxygen, a conductive material, and a binder.In one embodiment, for example, the first and second positive-electrodelayers 14 a and 14 b may be formed by mixing the electrolyte, thecatalyst, the conductive material and the binder with each other, andadding a solvent to the mixture to make positive-electrode slurry andthen drying the positive-electrode slurry.

Here, the electrolyte may include the lithium salt or the metal saltdescribed above. A porous carbonaceous material, a conductive metalmaterial, a conductive organic material, or a mixture thereof may beused as the conductive material. In one embodiment, for example, carbonblack, graphite, graphene, activated carbon, carbon fibers, and carbonnanotubes may be used as the carbonaceous material. The conductive metalmaterial may be, for example, in the form of metal powder. In oneembodiment, for example, platinum (Pt), gold (Au), silver (Ag), or anoxide of manganese (Mn), nickel (Ni), or cobalt (Co) may be used as thecatalyst. In one embodiment, for example, polytetrafluoroethylene(“PTFE”), polypropylene, polyvinylidene fluoride (“PVDF”), polyethylene,styrene-butadiene rubber, etc. may be used as the binder.

The first and second positive-electrode layers 14 a and 14 b may beformed to be porous so that the first and second positive-electrodelayers 14 a and 14 b may serve or function as gas-diffusion layers forabsorbing oxygen in the atmosphere. Alternatively, an additionalgas-diffusion layer may be further disposed on the first and secondpositive-electrode layers 14 a and 14 b.

FIG. 3 is a schematic cross-sectional view of a unit cell of a metal-airbattery according to another alternative embodiment.

Referring to FIG. 3, a unit cell 10″ may include a first gas-diffusionlayer 17 a disposed on a top surface of a first positive-electrode layer14 a, and a second gas-diffusion layer 17 b disposed on a bottom surfaceof a second positive-electrode layer 14 b. The first gas-diffusion layer14 a and the second gas-diffusion layer 14 b may extend to a first sidesurface of a negative-electrode metal layer 11 be continuously connectedto each other to surround the first side surface of thenegative-electrode metal layer 11.

The first and second gas-diffusion layers 17 a and 17 b absorb oxygen inthe atmosphere and provide the absorbed oxygen to the first and secondpositive-electrode layers 14 a and 14 b. To provide oxygen in theatmosphere to the first and second positive-electrode layers 14 a and 14b, the first and second gas-diffusion layers 17 a and 17 b may have aporous structure to smoothly diffuse oxygen from the outside. In oneembodiment, for example, the first and second gas-diffusion layers 17 aand 17 b may include or be formed of carbon paper, carbon cloth, orcarbon felt using carbon fiber, or may include or be formed of spongefoam metal or a metal fiber mat. Alternatively, the first and secondgas-diffusion layers 17 a and 17 b may include or be formed of aflexible porous material having non-conductive properties, such asnon-woven fabric.

FIG. 4 is a schematic cross-sectional view of a unit cell of a metal-airbattery according to another alternative embodiment.

Referring to FIG. 4, an embodiment of a unit cell 20 may include anegative-electrode metal layer 11, a first electrolyte film 12 adisposed on a top surface of the negative-electrode metal layer 11, afirst separation film 13 a disposed on a top surface of the firstelectrolyte film 12 a, a first positive-electrode layer 14 a disposed ona top surface of the first separation film 13 a, a second electrolytefilm 12 b disposed on a bottom surface of the negative-electrode metallayer 11, a second separation film 13 b disposed on a bottom surface ofthe second electrolyte film 12 b, and a second positive-electrode layer14 b disposed on a bottom surface of the second separation film 13 b.

In such an embodiment, as illustrated in FIG. 4, the first electrolytefilm 12 a and the second electrolyte film 12 b are separated or spacedapart from each other. In such an embodiment, the first separation film13 a and the second separation film 13 b are separated or spaced apartfrom each other, and the first positive-electrode layer 14 a and thesecond positive-electrode layer 14 b are separated or spaced apart fromeach other. In an alternative embodiment, the first separation film 13 aand the first electrolyte film 12 a may be formed in a single layer, andthe second separation film 13 b and the second electrolyte film 12 b maybe formed in a single layer. In such an embodiment, the first separationfilm 13 a between the first electrolyte film 12 a and the firstpositive-electrode layer 14 a, and the second separation film 13 bbetween the second electrolyte film 12 b and the secondpositive-electrode layer 14 b may be omitted.

The unit cell 20 may further include a sealing material 16 disposed on afirst side surface and a second side surface of the negative-electrodemetal layer 11 between the top and bottom surfaces of thenegative-electrode metal layer 11, and a negative-electrode currentcollector 15 connected to the second side surface of thenegative-electrode metal layer 11 and extending through the sealingmaterial 16. The sealing material 16 may seal the first side surface andthe second side surface of the negative-electrode metal layer 11 toprevent contact of the negative-electrode metal layer 11 with airoutside the unit cell 20. To fix the sealing material 16, the firstseparation film 13 a and the second separation film 13 b may extendbeyond the first and second side surfaces of the negative-electrodemetal layer 11. In such an embodiment, the first positive-electrodelayer 14 a and the second positive-electrode layer 14 b may extend orprotrude beyond the first and second side surfaces of thenegative-electrode metal layer 11. Thus, a gap or a space betweenprotruding portions of the first separation film 13 a and the secondseparation film 13 b may be filled with the sealing material 16. In anembodiment, where the first separation film 13 a and the secondseparation film 13 b are omitted, the first electrolyte film 12 a andthe second electrolyte film 12 b may extend beyond the first and secondside surfaces of the negative-electrode metal layer 11.

FIG. 5 is a schematic cross-sectional view of a unit cell of a metal-airbattery according to another alternative embodiment.

Referring to FIG. 5, an embodiment of a unit cell 20′ may furtherinclude a first gas-diffusion layer 17 a disposed on a top surface of afirst positive-electrode layer 14 a, and a second gas-diffusion layer 17b disposed on a bottom surface of the second positive-electrode layer 14b. The first gas-diffusion layer 17 a and the second gas-diffusion layer17 b may be separated or spaced apart from each other, and extend beyonda first side surface and a second side surface of a negative-electrodemetal layer 11.

In an embodiment, a metal-air battery may have a cylindrical shapeformed by winding the unit cell 10, 10′, 10″, 20, or 20′ described aboveinto a roll.

FIG. 6A is a perspective view of a metal-air battery having a rolledcylindrical shape formed by winding the unit cell 10 of FIG. 1 into aroll, and FIG. 6B is an enlarged view of the encircled portion of FIG.6A.

Referring to FIGS. 6A and 6B, an embodiment of a metal-air battery 100is a cylindrical metal-air battery having a rolled cylindrical shape inwhich the unit cell 10 wound into a roll. The unit cell 10 may be woundin a way such that the first side surface of the negative-electrodemetal layer 11 is located at the center of the roll and the second sidesurface of the negative-electrode metal layer 11 is located at anoutermost part of the roll. In such an embodiment, the first sidesurface of the negative-electrode metal layer 11 surrounded by theelectrolyte film 12, the separation film 13 and the positive-electrodelayer 14 may be located at a center portion or an innermost portion ofthe metal-air battery 100, and the second side surface of thenegative-electrode metal layer 11 connected to the negative-electrodecurrent collector 15 may be located at an outer side of the metal-airbattery 100.

In such an embodiment, where the unit cell 10 is wound into a roll toform a metal-air battery having a rolled cylindrical shape, the top andbottom surfaces of the negative-electrode metal layer 11 facing eachother are located in a circumferential direction of the roll, and thefirst electrolyte film 12 a, the first separation film 13 a, the firstpositive-electrode layer 14 a, the second electrolyte film 12 b, thesecond separation film 13 b and the second positive-electrode layer 14 bare also located in the circumferential direction of the roll. The firstpositive-electrode layer 14 a on the top of the unit cell 10 and thesecond positive-electrode layer 14 b on the bottom of the unit cell 10may contact each other while facing each other when the unit cell 10 iswound. In an embodiment where the unit cell 10″ of FIG. 3 is used, thefirst gas-diffusion layer 17 a and the second gas-diffusion layer 17 bmay contact each other while facing each other when the unit cell 10″ iswound.

FIG. 7 is a perspective view of a metal-air battery having a rolledcylindrical shape formed by winding the unit cell 20 of FIG. 4 into aroll.

Referring to FIG. 7, an embodiment of a metal-air battery 110 is acylindrical metal-air battery with the unit cell 20 wound into a roll.In such an embodiment, the unit cell 20 may be wound in a way such thatthe second side surface of the negative-electrode metal layer 11connected to the negative-electrode current collector 15 is located atan outer side of the metal-air battery 110 and the first side surface ofthe negative-electrode metal layer 11 is located at an inside of themetal-air battery 110.

FIG. 8 is a cross-sectional view of a metal-air battery including anouter casing.

Referring to FIG. 8, an embodiment of the metal-air battery 100 mayfurther include an outer casing 101 wrapping around the wound unit cell10 to protect the unit cell 10. In an embodiment, as shown in FIG. 8,the wound unit cell 10 of FIG. 1 may be wrapped with the outer casing101, but not being limited thereto. In an alternative embodiment, thewound unit cell 20 of FIG. 4 may be wrapped with the outer casing 101.

According to embodiments, as described above, the metal-air battery 100or 110 may be manufactured in a cylindrical shape to minimize the areasof the outer casing 101 and the negative-electrode current collector 15.Thus, in such embodiments, the metal-air battery 100 or 110 may bedecreased in weight and improved in energy density. In such embodiments,the first electrolyte film 12 a and the second electrolyte film 12 b andthe first positive-electrode layer 14 a and the secondpositive-electrode layer 14 b may be arranged on opposite surfaces ofone negative-electrode metal layer 11 and be symmetrical with eachother. Thus, the areas of electrodes may be increased to significantlyimprove energy density. Furthermore, in such embodiments, the metal-airbatteries 100 and 110 have a cylindrical shape and may be thusmanufactured as 18650 type batteries. Accordingly, such embodiments ofthe metal-air battery 100 or 110 may be used in many differentapplications and may replace another type of battery.

FIG. 9 is a graph showing energy density of the metal-air battery 100 ofFIG. 6 according to an embodiment and energy density of a conventionalmetal-air battery. In FIG. 9, a variation in energy density of aconventional metal-air battery having a general planar two-dimensional(“2D”) cell shape versus the number of cells and a variation in energydensity of an embodiment of the metal-air battery 100 versus the numberof cells are compared with each other.

Referring to FIG. 9, the energy density of the conventional metal-airbattery (2D cell) hardly changed even when the number of cells wasincreased. In contrast, the energy density of an embodiment of themetal-air battery 100 (Coaxial cell) increased as the number of cellswas increased. When the number of cells was one, the energy density ofan embodiment of the metal-air battery 100 (Coaxial cell) was abouteight times higher than that of the conventional metal-air battery (2Dcell). When the number of cells was twenty, an embodiment of themetal-air battery 100 (Coaxial cell) was about ten times higher thanthat of the conventional metal-air battery (2D cell).

FIG. 10 is a schematic cross-sectional view of a unit cell of ametal-air battery according to another alternative embodiment.

Referring to FIG. 10, in an embodiment, a first positive-electrode layer14 a of a unit cell 20″ may include a plurality of positive-electrodeplates 14′ arranged along a top surface of a first separation film 13 a,and a second positive-electrode layer 14 b may include a plurality ofpositive-electrode plates 14′ arranged on a bottom surface of a secondseparation film 13 b. In such an embodiment, a gap 19 is defined betweeneach of two adjacent positive-electrode plates 14′. In such anembodiment, when the unit cell 20″ is wound into a roll, the radius ofcurvature between inner and outer sides of the roll changes and thus theplurality of positive-electrode plates 14′ and gaps 19 therebetween mayeffectively prevent the first and second positive-electrode layers 14 aand 14 b from being damaged.

FIG. 11 is a cross-sectional view of a part of a metal-air batteryhaving a rolled cylindrical shape formed by winding the unit cell 20″ ofFIG. 10 into a roll.

Referring to FIG. 11, in an embodiment, when the unit cell 20″ is woundinto a roll, the plurality of positive-electrode plates 14′ and gaps 19therebetween may be arranged in a circumferential direction of the roll.When the unit cell 20″ is wound, the positive-electrode plates 14′ ofthe first positive-electrode layer 14 a and the positive-electrodeplates 14′ of the second positive-electrode layer 14 b may contact eachother while facing each other. Here, the positive-electrode plates 14′of the second positive-electrode layer 14 b may be arranged across thegaps 19 of the first positive-electrode layer 14 a to connect twoadjacent positive-electrode plates 14′ of the first positive-electrodelayer 14 a. Thus, current may smoothly flow between the firstpositive-electrode layer 14 a and the second positive-electrode layer 14b. The lengths of the positive-electrode plates 14′ and the gaps 19 maybe determined to be not uniform when the unit cell 20″ is wound, suchthat the gaps 19 of the second positive-electrode layer 14 b and thegaps 19 of the first positive-electrode layer 14 a do not coincide witheach other and the positive-electrode plates 14′ of the secondpositive-electrode layer 14 b connect two adjacent positive-electrodeplates 14′ of the first positive-electrode layer 14 a to each other.

FIG. 12 is a schematic cross-sectional view of a unit cell of ametal-air battery according to another alternative embodiment.

Referring to FIG. 12, a unit cell 30 may include a negative-electrodemetal layer 11 having a cylindrical shape, a first electrolyte film 12 adisposed on an outer circumference surface of the negative-electrodemetal layer 11, a first separation film 13 a disposed on an outercircumference surface of the first electrolyte film 12 a, a firstpositive-electrode layer 14 a disposed on an outer circumference surfaceof the first separation film 13 a, a second electrolyte film 12 bdisposed on an inner circumference surface of the negative-electrodemetal layer 11, a second separation film 13 b disposed on an innercircumference surface of the second electrolyte film 12 b, and a secondpositive-electrode layer 14 b disposed on an inner circumference surfaceof the second separation film 13 b. In such an embodiment, thenegative-electrode metal layer 11, the first electrolyte film 12 a, thefirst separation film 13 a, the first positive-electrode layer 14 a, thesecond electrolyte film 12 b, the second separation film 13 b and thesecond positive-electrode layer 14 b may be arranged in a concentricform to have the same central axis. In such an embodiment, the secondseparation film 13 b may surround the second positive-electrode layer 14b, the second electrolyte film 12 b may surround the second separationfilm 13 b, the negative-electrode metal layer 11 may surround the secondelectrolyte film 12 b, the first electrolyte film 12 a may surround thenegative-electrode metal layer 11, the first separation film 13 a maysurround the first electrolyte film 12 a, and the firstpositive-electrode layer 14 a may surround the first separation film 13a.

In such an embodiment, as described above, the first separation film 13a and the first electrolyte film 12 a may be formed in a single layer,and the second separation film 13 b and the second electrolyte film 12 bmay be formed in a single layer. In such an embodiment, the firstpositive-electrode layer 14 a may be disposed on the outer circumferencesurface of the first electrolyte film 12 a, and the secondpositive-electrode layer 14 b may be disposed on the inner circumferencesurface of the second electrolyte film 12 b.

FIG. 13 is a cross-sectional view of a metal-air battery including theunit cell 30 of FIG. 12.

Referring to FIG. 13, an embodiment of a metal-air battery 120 mayinclude a plurality of cylindrical units cells 30 arranged in aconcentric form. FIG. 13 illustrates the metal-air battery 120 includingtwo unit cells 30, for convenience of illustration, but the metal-airbattery 120 may include three or more unit cells 30. Twonegative-electrode metal layers 11 may each have an outer circumferencesurface and an inner circumference surface facing each other andarranged in a circumferential direction. A first electrolyte film 12 a,a first separation film 13 a and a first positive-electrode layer 14 amay be sequentially arranged on each of the outer circumference surfacesof the two negative-electrode metal layers 11. A second electrolyte film12 b, a second separation film 13 b and a second positive-electrodelayer 14 b may be sequentially arranged on each of the innercircumference surfaces of the two negative-electrode metal layers 11. Insuch an embodiment, the second positive-electrode layer 14 b on aninnermost part of the metal-air battery 120 may have a cylindricalshape, the center of which is not hollow or is hollow. Among the twoadjacent unit cells 30, the first positive-electrode layer 14 a of theinner unit cell 30 and the second positive-electrode layer 14 b of theouter unit cell 30 may share a common positive-electrode plate. Themetal-air battery 120 may further include an outer casing 101surrounding the first positive-electrode layer 14 a of the outermostunit cell 30.

FIG. 14 is a schematic cross-sectional view of a unit cell of ametal-air battery according to another alternative embodiment.

Referring to FIG. 14, in an embodiment, a unit cell 40 may include anegative-electrode metal layer 11 having a segment shape obtained bydividing a cylinder into several parts. The negative-electrode metallayer 11 may have an outer circumference surface and an innercircumference surface facing each other and arranged in acircumferential direction, and two side surfaces connecting the outercircumference surface and the inner circumference surface. The two sidesurfaces may be located, for example, in a direction of a diameter ofthe metal-air battery. In such an embodiment, a first electrolyte film12 a and a second electrolyte film 12 b may be connected to each otherto surround the two side surfaces of the negative-electrode metal layer11. In such an embodiment, a first separation film 13 a and a secondseparation film 13 b may be connected to each other to surround the twoside surfaces of the negative-electrode metal layer 11, and a firstpositive-electrode layer 14 a and a second positive-electrode layer 14 bmay be connected to each other to surround the two side surfaces of thenegative-electrode metal layer 11.

FIG. 15 is a cross-sectional view of a metal-air battery including theunit cell 40 of FIG. 14.

Referring to FIG. 15, an embodiment of a metal-air battery 130 mayinclude a plurality of cylindrical parts 130 a, 130 b, 130 c, and 130 darranged in a concentric form to share a central axis. In oneembodiment, for example, a unit cell 30 having the cylindrical shape ofFIG. 12 may be arranged as the innermost first cylindrical part 130 a. Aplurality of unit cells 40 having the segment shape of FIG. 14 may bearranged as the second, third and fourth cylindrical parts 130 b, 130 cand 130 d in a circumferential direction. The metal-air battery 130 mayfurther include an outer casing 101 surrounding the outermost fourthcylindrical part 130 d. In the metal-air battery 130 of FIG. 15, a firstpositive-electrode layer 14 a and a second positive-electrode layer 14 bare arranged in a direction of a diameter thereof. Accordingly, in suchan embodiment, the areas of surfaces of the first positive-electrodelayer 14 a and the second positive-electrode layer 14 b may increase,thereby substantially increasing energy density of the metal-air battery130.

The metal-air battery 130 of FIG. 15 may include a unit cell 30 having acylindrical shape and a plurality of unit cells 40 having a segmentshape in various combinations. In one embodiment, for example, one unitcell 30 having a cylindrical shape may be arranged as each of the firstand third cylindrical parts 130 a and 130 c, and a plurality of unitcells 40 having a segment shape may be arranged as the second and fourthcylindrical parts 130 b and 130 d in the circumferential direction.Alternatively, only a plurality of unit cells 40 having a segment shapemay be arranged on the first to fourth cylindrical parts 130 a, 130 b,130 c, and 130 d. In an embodiment, as shown in FIG. 15, the metal-airbattery 130 may include four cylindrical parts 130 a, 130 b, 130 c, and130 d, but not being limited thereto. Alternatively, the metal-airbattery 130 may include two, three, five, or more cylindrical parts. Ifan embodiment of the metal-air battery 130 includes only two cylindricalparts and only the unit cell 30 having a cylindrical shape is arrangedon each of the two cylindrical parts, such an embodiment of themetal-air battery 130 may substantially be the same as the metal-airbattery 120 of FIG. 13.

An embodiment of the metal-air battery 100, 110, 120 or 130 describedabove may be easily stacked to manufacture a battery module in aconvenient manner. Hereinafter, embodiments of a battery moduleincluding the metal-air battery will be described.

FIG. 16 is a perspective view illustrating a state in which a pluralityof metal-air batteries 100 is stacked, according to an embodiment.

Referring to FIG. 16, in an embodiment, the plurality of metal-airbatteries 100 may be stacked in a way such that central axes thereof donot coincide with another and are parallel with one another and outercircumference surfaces thereof are in contact with one another. AlthoughFIG. 16 illustrates that a type of metal-air battery 100 having a unitcell 10 wound into a roll is stacked, other type of the metal-airbattery 110, 120, or 130 may be stacked. Alternatively, the varioustypes of the metal-air battery 100, 110, 120 and 130 may be stacked invarious combinations.

FIG. 17 is a cross-sectional view illustrating a state in which thestacked metal-air batteries 100 of FIG. 16 are packaged.

Referring to FIG. 17, the stacked metal-air batteries 100 are packagedby wrapping outer circumference surfaces thereof with an outer casing101, thereby obtaining a battery module 200.

FIG. 18 is a perspective view illustrating a state in which a pluralityof metal-air batteries 100 is stacked, according to an alternativeembodiment.

Referring to FIG. 18, in an alternative embodiment, the plurality ofmetal-air batteries 100 may be stacked in a way such that central axesthereof coincide with one another. In such an embodiment, a flat bottomsurface of each of two adjacent metal-air batteries 100 may be incontact with a flat top surface of the other. Although FIG. 18illustrates that the plurality of metal-air batteries 100 each havingone unit cell wound into a roll are stacked, another type of metal-airbattery 110, 120 or 130 may be stacked. Alternatively, various types ofmetal-air battery 100, 110, 120 and 130 may be stacked in combination.

Some embodiments of the cylindrical metal-air battery have beendescribed above with reference to the accompanying drawings but aremerely exemplary. It would be apparent to those of ordinary skill in theart that various changes may be made thereto without departing from theprinciples and spirit of the inventive concept, the scope of which isdefined in the claims and their equivalents. It should be understoodthat the embodiments described herein should be considered in adescriptive sense only and not for purposes of limitation. Descriptionsof features or aspects within each embodiment should typically beconsidered as available for other similar features or aspects in otherembodiments.

What is claimed is:
 1. A metal-air battery comprising a unit cell woundinto a roll, wherein the unit cell comprises: a negative-electrode metallayer having a first surface located in a circumferential direction ofthe roll, and a second surface facing the first surface and located inthe circumferential direction of the roll; a first electrolyte film anda first positive-electrode layer sequentially disposed on the firstsurface of the negative-electrode metal layer; a second electrolyte filmand a second positive-electrode layer sequentially disposed on thesecond surface of the negative-electrode metal layer; a firstgas-diffusion layer disposed on the first positive-electrode layer; anda second gas-diffusion layer disposed on the second positive-electrodelayer, wherein the first gas-diffusion layer and the secondgas-diffusion layer are continuously connected to each other, whereinthe unit cell is wound in a way such that the first positive-electrodelayer and the second positive-electrode layer face each other.
 2. Themetal-air battery of claim 1, wherein the first electrolyte film and thesecond electrolyte film are continuously connected to each other, andthe first positive-electrode layer and the second positive-electrodelayer are continuously connected to each other.
 3. The metal-air batteryof claim 2, wherein the negative-electrode metal layer has a thirdsurface between the first surface and the second surface, and a fourthsurface facing the third surface, and the first electrolyte film and thesecond electrolyte film are connected to each other to surround thethird surface of the negative-electrode metal layer.
 4. The metal-airbattery of claim 3, wherein the first positive-electrode layer and thesecond positive-electrode layer are connected to each other to surroundthe third surface of the negative-electrode metal layer.
 5. Themetal-air battery of claim 3, wherein the unit cell further comprises: afirst separation film disposed between the first electrolyte film andthe first positive-electrode layer; and a second separation filmdisposed between the second electrolyte film and the secondpositive-electrode layer, wherein the first separation film and thesecond separation film are continuously connected to each other tosurround the third surface of the negative-electrode metal layer.
 6. Themetal-air battery of claim 3, wherein the unit cell further comprises anegative-electrode current collector connected to the fourth surface ofthe negative-electrode metal layer.
 7. The metal-air battery of claim 3,wherein the unit cell further comprises a sealing material which sealsthe fourth surface of the negative-electrode metal layer.
 8. Themetal-air battery of claim 3, wherein the unit cell is wound in the waysuch that the third surface of the negative-electrode metal layer islocated at a center of the roll and the fourth surface of thenegative-electrode metal layer is located at an outermost part of theroll.
 9. The metal-air battery of claim 2, wherein the unit cell iswound in the way such that the first gas-diffusion layer and the secondgas-diffusion layer face each other.
 10. The metal-air battery of claim1, wherein the first electrolyte film and the second electrolyte filmare spaced apart from each other, and the first positive-electrode layerand the second positive-electrode layer are spaced apart from eachother.
 11. The metal-air battery of claim 10, wherein thenegative-electrode metal layer has a third surface between the firstsurface and the second surface, and a fourth surface facing the thirdsurface, the first and second positive-electrode layers extend beyondthe third and fourth surfaces of the negative-electrode metal layer. 12.The metal-air battery of claim 11, wherein the unit cell furthercomprises: a first separation film disposed between the firstelectrolyte film and the first positive-electrode layer; and a secondseparation film disposed between the second electrolyte film and thesecond positive-electrode layer, wherein the first and second separationfilms are spaced apart from each other, and extend beyond the third andfourth surfaces of the negative-electrode metal layer.
 13. The metal-airbattery of claim 11, wherein the unit cell further comprises a sealingmaterial which seals the third and fourth surfaces of thenegative-electrode metal layer.
 14. The metal-air battery of claim 13,wherein the unit cell further comprises a negative-electrode currentcollector connected to the fourth surface of the negative-electrodemetal layer and extending through the sealing material.
 15. Themetal-air battery of claim 1, wherein the first positive-electrode layercomprises a plurality of first positive-electrode plates arranged in thecircumferential direction of the roll, wherein a first gap is definedbetween each two adjacent first positive-electrode plates, the secondpositive-electrode layer comprises a plurality of secondpositive-electrode plates arranged in the circumferential direction ofthe roll, wherein a second gap is defined between each two adjacentsecond positive-electrode plates, wherein the roll is wound in the waysuch that the second positive-electrode plates connect the two adjacentfirst positive-electrode plates across the first gap.
 16. The metal-airbattery of claim 1, wherein the metal-air battery comprises a pluralityof unit cells wound into the roll, wherein the plurality of unit cellsare stacked in a way such that central axes of the roll do not coincidewith one another and outer circumference surfaces of the roll are incontact with one another.
 17. The metal-air battery of claim 1, whereinthe metal-air battery comprises a plurality of unit cells wound into theroll, wherein the plurality of unit cells are stacked in a way such thatcentral axes of the roll coincide with one another.